By controlling the reaction conditions, glacial acetic acid can also be produced by the same reaction. Because carbon monoxide and methanol are commonly used chemical raw materials, methyl carbonylation has always been favored. As early as 1925, the British Celanese Company developed the first pilot plant for methyl carbonylation to produce acetic acid. However, the application of this method has been limited due to the lack of containers that can withstand high pressure (200 atm or higher) and corrosion resistance. In 1963, the German BASF Chemical Company used cobalt as a catalyst to develop the first process suitable for industrial production of glacial acetic acid. In 1968, the rhodium catalyst greatly reduced the difficulty of the reaction. Using a catalyst system composed of rhodium carbonyl compound and iodide, methanol and carbon monoxide are reacted in a water-acetic acid medium at 175°C and a pressure lower than 3 MPa to obtain an acetic acid product.
Because the activity and selectivity of the catalyst are relatively high, there are few by-products of the reaction. The low-pressure carbonylation of methanol to produce acetic acid has the advantages of cheap raw materials, mild operating conditions, high acetic acid yield, good product quality and simple process flow. However, the reaction medium is severely corrosive and special corrosion-resistant materials need to be used. In 1970, the United States Monsanto Company built a device using this process, so rhodium-catalyzed methyl carbonylation to acetic acid gradually became the dominant Monsanto method. In the late 1990s, BP successfully commercialized the Cativa catalytic method. This method uses a ruthenium catalyst and uses ([Ir(CO)₂I₂]), which is greener and more efficient than the Monsanto method.